Talking about the comprehensive lightning protection of SPC Exchange

Now many units have installed the program-controlled switchboard, and the most important part of the program-controlled switchboard is integrated circuit (IC). IC anti-interference ability is low, even if from the line induction Lightning electromagnetic pulse (LEMP), can also penetrate IC components. Therefore, the program-controlled switches are prone to lightning accidents. The most damaged parts are the relay board, the user board, the billing card and the power supply section. Because of the value of these motherboards, in order to reduce economic losses, some users want to do a variety of ways to protect the switch, and even the entire switch to insurance companies, but due to lightning caused by the loss of communication interruption, but can not be compensated. Therefore, the program-controlled exchange of lightning protection appears particularly important.

Then how to prevent the program-controlled exchange of lightning? The author thinks that should consider from the following several aspects synthetically.

Identification of minefields within buildings (LPZ)

According to the International Electrotechnical Commission iec1312-1 "Lightning Electromagnetic pulse protection" of the relevant provisions, the building is divided into 4 districts (Fig 1): Lpzoa area, the objects in this area may be directly struck by lightning, the area of the electromagnetic field does not decay; Lpzob area, the object in this area cannot be directly struck by lightning, There is no attenuation of electromagnetic field in the area; LPZ1 area, the object in this area cannot be directly struck by lightning, and the electromagnetic field in the area may decay; The LPZ2 area is a follow-up mine-protection area. According to the above zoning principle, we should put the SPC in the LPZ2 area as far as possible in order to reduce the influence of lightning electromagnetic pulse on the switch.

Determine the equipotential connection of the switch

The purpose of the switch equipotential connection is to reduce the potential difference between various metal parts and systems in the space where lightning protection is needed. A equipotential connection should be made at the junction of the mine-protection area by requiring metal components and systems at the junction of the minefields, as well as metal components and systems within a mine-protection area (Fig. 1). such as in the Lightning Protection Area Lpzo and LPZ1 junction of the Equipotential connection belt, will all enter the switch room metal conductor should do equipotential connection. In addition, these lines should be installed at the junction of LPZ1 and LPZ2 SPD.

Determine the location of the engine room

The location of the computer room should be combined with the far and near planning of the construction project and the terrain position. For high-rise buildings, the general practice is to set the computer room in the 4 floor below the first floor space. In humid areas, the first floor is not suitable for telephone exchange room. However, some units are restricted by the conditions, not according to the above principles of the switch room, such as the Guangdong Guest House of the program-controlled rooms in the building on the floor of the storey room. According to the relevant provisions of the iec1312-1 "Lightning Electromagnetic pulse Protection", the section of the building is divided into the Lpzob area in the Lightning protection area, in which the electromagnetic field does not decay, and the switch is greatly influenced by the electromagnetic field.

Determine the grounding system of the switch

The earthing of the program-controlled switchboard includes: The DC power supply grounding, the telecommunication equipment chassis or the frame shielding earthing, the metal sheath or shielding earthing of the inbound communication cable, the grounding of the Open-wire or the cable inbound arrester and the grounding of the signal cable's blank line. In order to do a good grounding of the program-controlled switchboard, some units for the program-controlled switchboard to do a pair of artificial polar, polar grounding resistance is also in line with the requirements of the standard, but the site and the building of the lightning grounding due to the limitations of the site by less than 20m. such as Guangzhou Yunfu Hotel and South China Building general room of the artificial polar and building lightning protection grounding are less than 20m, not in accordance with the state jgj/t16-92 "Civil Architecture Electrical Design Code" on both the network must be greater than 20m when the relevant provisions. In order to solve the above problems, the common practice is to connect all the earthing of the program-controlled switchboard with the communication grounding device shared by the whole station, and then connect the common grounding device with the lightning-proof grounding of the building, and make the poles together. After the use of the polar poles, the grounding device of communication equipment needs to use a dedicated grounding trunk, the section area of the trunk is not less than 25mm2 copper conductor.

Ways to determine wiring

At present, the transmission network of the switch is using two methods, aerial and buried. The overhead cable should be the telephone line or cable buried in the front of the house, buried length >2ρ (the resistivity of the ground resistance, the unit is ω*m), the actual length of >50m. And buried in general is the use of metal armored cable directly buried, or non-metallic shielded cable through metal pipe directly buried. From the point of view of lightning, in the case of a condition of the cable should choose to bury the way. The transmission network of the SPC exchange should be routed along the special signal cable slot in the room, avoid laying along the structure column of the building or close to the external wall, and the weak and strong electric cable should not be laid in the same slot to reduce the interference. such as a central building in Guangzhou without a dedicated signal cable trough, its signal line and power cord is the same groove laying, when the power line is struck by lightning or induction of lightning electric pulse, will be in the signal line also induction of an electromagnetic pulse, and along the signal line to the switch, so that the switch by lightning. Therefore, the central building's switchboard and computer network systems are often struck by lightning.

Shield of the switch

Switch shielding (including space and line shielding) in addition to signal lines and power lines, the switch room should also be shielded treatment, the specific approach is to metal doors, windows, ceiling keel and anti-static special floor grounding.

Measures for determining the pressure of shunt

In the power supply, three-stage shunt pressure limiting measures should be adopted to minimize the amplitude of lightning electromagnetic pulse. Therefore, the first stage is located at the low-voltage portion of the main distribution room, installation of 40kA power Lightning box, the second level is located in the floor of the Power box, the installation of 20kA power supply lightning box; the third level is located in the Switch Room power switch, install 10kA power supply Lightning box, or before UPS installation of a level of power to avoid lightning box. In the signal aspect, also should adopt the shunt limit pressure the measure. First of all, in the trunk and user line installed performance-controlled PBX arrester, the switch and billing terminals installed network Lightning arrester.

In short, the program-controlled switches can not focus on either side, which side of the lightning protection can only be called local lightning, and local lightning with "congenitally deficient" problem. Therefore, the program-controlled switchboard Lightning protection should be integrated.